US EPA

Lumbricus terrestris were exposed to malathion for 72 hours using either a filter paper or a laboratory based soil exposure system. Exposure concentrations (0 µg/cm2, 1 µg/cm2, 2 µg/cm2, 5 µg/cm2, 50 µg/cm2, 100 µg/cm2) included environmentally relevant doses. The EC50 for neurological signs as well as malathion/malaoxon earthworm body burdens (ppm) were determined for each exposure regime. Body burdens of malathion in L. terrestris were significantly higher after filter paper contact than after soil exposure at exposure concentrations 50µg/cm2 and 100 µg/cm2. The filter paper exposure resulted in a lower EC50 (between 2 µg/cm2 and 5 µg/cm2) than the soil exposures (> 100 µg/cm2). There were no detectable body burdens of malaoxon as a result of either exposure method. This paper demonstrates that different exposure methods can affect malathion body burden results and the development of clinical signs.

Journal Article

HENSON-RAMSEY, H., S. KENNEDY-STOSKOPF, J. LEVINE, D. SHEA, S. TAYLOR, AND M. K. STOSKOPF. A Comparison Of Two Exposure Systems To Apply Malathion To Lumbricus Terrestris (Journal Article). BULLETIN OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY. Springer, New York, NY, 78(6):427-431, (2007).